The present invention relates in general to an electronically controlled mask shield for use with a wave soldering machine to protect portions of circuit modules, such as gold contacts, during a wave soldering operation.
In the mass production of printed circuit modules, printed wiring boards (PWBs) are passed through a soldering apparatus wherein one side of the PWBs is subjected to a soldering operation to solder hundreds of terminals on each of the boards. The use of wave soldering machines for this purpose is well known. These machines include conveyors which carry the PWBs over a molten bath of solder that is agitated to rise in waves against the undersides of the PWBs.
One of the problems presented by the wave soldering process is that of protecting portions of the PWBs from being contacted by the hot molten solder. In particular, a plurality of gold contacts are disposed on PWBs which are used to connect the circuit board components to other boards or connectors. These gold contacts must be protected from the molten solder because it will contaminate or degrade the contacts.
One solution to this problem has been to install shields on the wave soldering machines which prevent the molten solder from contacting the gold contact areas of the PWBs. Typically, these shields are mechanically bolted in place on the wave soldering machines when they are needed. This requires that an operator gain access to the interior of the wave soldering machine, bolt the shield into place, and make manual adjustments to properly align the shield. The alignment procedure often requires that a PWB be passed through the wave soldering machine to check the alignment accuracy Once the wave soldering operation is completed, the shield must once again be manually removed. This entire procedure takes a considerable amount of time. In addition, environmental and safety concerns have led to the advent of fully enclosed wave soldering machines which cannot be easily accessed. As a consequence, the use of a manually attached and adjustable solder shield with such a machine is made extremely difficult and inconvenient, if not altogether impossible.